A prime which is the reverse concatenation of the first n triangular numbers

 
 
The sequence of triangular numbers
1, 3, 6, 10, 15, 21, 28, 36, 45, 55, 66, 78, 91, 105, 120, 136, 153, 171, 190, 210, 231, 253, 276, …

 

631   is a prime number.

10631   is a prime number.

55453628211510631   is a prime number.

786655453628211510631   is a prime number.

10591786655453628211510631   is a prime number.
 

What comes next?
 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

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About benvitalis

math grad - Interest: Number theory
This entry was posted in Number Puzzles and tagged . Bookmark the permalink.

One Response to A prime which is the reverse concatenation of the first n triangular numbers

  1. Paul says:

    The next example is the concatenation of the triangular numbers from 1 to the 1201, the resulting prime has 6560 digits. The prime starts

    721801720600…..510631

    The triangular number with index 1201 is 721801

    If anyone wants to see the prime its available here https://www.dropbox.com/s/761r6flmg54wwum/1201%20prime.txt?dl=0

    Paul.

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